Client side PID translation

Abstract

In a system that provides decoding of A/V streams, this invention reduces switching delays between different streams by modifying the Program Identification (PID) values of the Audio and Video data to respective PID values that are already known by the decoder. This technique allows the decoder to stay in a run state when switching between A/V streams, thereby reducing channel change times.

1. In a multimedia content delivery system where a subscriber terminal (ST) commences rendering multimedia entertainment content of a channel, the channel comprising a plurality of elementary streams, only upon receipt of a specified milestone protocol data unit (PDU), a method of reducing a length of a channel change operation between leaving a currently viewed channel and joining a new channel, comprising:
 predefining, with a decoder, on initialization, a plurality of distinct program identification (PID) values, each predefined PID value corresponding to a type elementary stream, wherein each of the elementary streams consists of either audio data, video data, or other related data; 
 identifying all of the elementary streams of said new channel, wherein said elementary streams comprise a plurality of PDUs including at least one of said specified milestone PDU; 
 changing, in all PDUs, a current PID value of each said elementary stream to the predefined PID value for the type of each said elementary stream; and 
 at a decoder of said ST, decoding said PDUs with said predefined PID values, as said PDUs arrive at said decoder, wherein said decoder is maintained in a running state during said channel change operation. 
 
     
     
       2. The method of  claim 1 , said identifying step further comprising:
 buffering all said PDUs of said new channel in a memory at an input buffer of said ST, before sending said PDUs to said decoder; 
 identifying in said memory a PDU carrying a program specific information regarding said new channel; and 
 based on said program specific information, identifying said current PID values used by each said elementary stream of said new channel. 
 
     
     
       3. The method of  claim 2 , wherein said multimedia entertainment content is carried in a Moving Picture Experts Group (MPEG) transport stream. 
     
     
       4. The method of  claim 3 , wherein said program specific information includes a program association table PAT and a program map table PMT, and wherein said PAT identifies said new channel and said PMT identifies said elementary streams of said new channel. 
     
     
       5. The method according to  claim 1 , said changing step further comprising:
 replacing said current PIP values in all said PDUs in an input buffer for said new channel with said predefined PID values. 
 
     
     
       6. The method of  claim 1 , said decoding step further comprising:
 extracting from an input buffer said PDUs that have said predefined PIP values, 
 decoding said PDUs that have said predefined PIP values to obtain said multimedia entertainment content, and 
 providing said multimedia entertainment to a user of said ST. 
 
     
     
       7. A system that reduces switching delays for multimedia channels, the system comprising:
 a server side that receives encoded multimedia streams having a plurality of milestones; and 
 a client side that receives said multimedia streams from said server side, said client side comprising:
 an input buffer that stores said multimedia streams until a milestone is detected, 
 a program and system information (PSI) controller, coupled to said input buffer, that detects said milestones in said multimedia streams, wherein each multimedia stream comprises a plurality of elementary streams, and changes a current program identification (PID) value in each of the elementary streams in said multimedia streams to a predefined PID value, wherein the predefined PID value corresponds to a type of elementary stream, wherein the elementary streams consist of either audio data, video data, or other related data, and 
 
 a decoder that predefines, on initialization, the predefined PID values for each of the types of elementary stream, and converts said multimedia streams from said PSI controller into audio and video information for display. 
 
     
     
       8. A program and system information (PSI) controller that modifies program identifiers (PIDs) in multimedia streams, wherein each multimedia stream comprises a plurality of elementary streams, each elementary stream consisting of one type of data, said PSI controller comprising:
 means for modifying a Program Association Table (PAT), said PAT determining which programs exist in said multimedia streams; 
 means for modifying Program Map Tables (PMTs), identified by said PAT, that point to PIDs of data in said multimedia streams; and 
 a PID change unit that changes a current PID value in each of the elementary streams in said multimedia streams to a predefined PID value, wherein the predefined PID value corresponds to said one type of data, wherein the types of data include audio, video, and other related data.